Before World War II, American higher education was dominated by four-year undergraduate education. Although research universities and community colleges have emerged, they have always been on the two wings of the American higher education system. However, this situation changed after World War II. Due to the vital contribution made by research universities in military technology research and development during the war and the crisis consciousness brought by Soviet satellites, the federal government began to vigorously support research universities, develop postgraduate education, and encourage scientific research in universities, especially basic scientific research.

Since then, research universities have entered a new historical development period. ? Scientific research and postgraduate education are the symbolic features of research universities and the source of their livelihood. The development of post-war research universities is mainly reflected in the strengthening of scientific research functions and the development of "quantity" and "quality" of postgraduate education. Among them, the strengthening of scientific research function is a great driving force for the rapid development of American research universities after the war, which not only makes research universities the core of American scientific research system, but also brings a lot of funds for the development of research universities.

With the rapid development of scientific research in colleges and universities, graduate education has also entered the heyday of development. The shortage of teachers brought by the popularization of higher education, the increase of federal funding for scientific research and graduate students, and the large demand for senior professionals engaged in basic research and applied research by economic development have greatly promoted the development of graduate education. By 1958, the number of universities offering postgraduate courses in the United States increased sharply, from 300 in 1940 to 569 in 1958, and from 100 to/kloc. Compared with 1939/ 1940, the number of master's degree awards increased by 1.6 times, and the number of doctoral degree awards increased by 2.8 times [26]. By 1975, the number of graduate students in the United States reached1260,000, more than four times that of 1950.

Its growth rate far exceeds the growth rate of undergraduates in this period, especially in some major research universities, the number of graduate students even exceeds the number of undergraduates, accounting for more than half of the total number of students in the school. As Nathan M.Pusey, the former president of Harvard University, said, "The reputation of American higher education in this period is more due to the progress of postgraduate education (including postdoctoral), scientific research and research training than undergraduates." "The great era of American graduate schools has finally arrived. The United States trained more highly educated scholars in the 1960s than in the first 60 years of the 20th century combined. The graduate school finally surpassed the undergraduate college and became the main institution of American higher education. "